You can comment on posts and reply to comments using this option.
1. In the Home screen, tap the icon for the post on which you want to comment.
The Comments screen is displayed.
3. To comment on the post, enter your comment in the Add a comment field and tap -> icon.
Your comment is posted.
4. To reply to a comment, tap Reply in the row of the comment, enter your comment in the Add a comment field, and tap the -> icon.
Your reply is posted.